73 



NOTES ON SOME DISTINCTIVE POINTS IN THE PUPAE OP 

 WEST AFRICAN MOSQUITOS. 



By A. Ingram, M.D., CM., and J. W. Scott Macfie, M.A.,. D.Sc, 



West African Medical Staff. 



Wesche employed the relative length of the trumpets to the length of the thorax 

 and the shape of the openings of the trumpets in drawing up a Key to the Pupae 

 of West African Culicidae (Bull. Ent. Res., i, pp. 18-19). Howard, Dyar and Knab 

 in their valuable monograph " The Mosquitoes of North and Central America and 

 the West Indies " (Vol. i, pp. 102-103) state that in their experience too much 

 has been made of the difference between the pupal trumpets of Anopheles and 

 Culex ; the variations in the shape, size, and length of the breathing trumpets 

 between different species are numerous, they say, but " furnish no characteristics 

 which are diagnostic of genera or larger groups." They consider that there are 

 intermediate forms and that differences between species are frequently more 

 striking than between genera themselves. They remark also that this may 

 equally well apply to the differences in shape of the pupal paddles, admitting, 

 however, that " there is a striking difference between the two tribes Culicini and 

 Sabethini " as regards the paddles for " In the Culicini the paddles are large, 

 broad and rounded in outline ; they are strengthened by a stout longitudinal mid- 

 rib which bears a spine or seta apically. In the Sabethini the paddles are much 

 smaller, narrower and tapered to a point ; the midrib is either absent or poorly 

 developed and there is no spine or seta." It may be remarked here that in 

 Eretmojpodites, the only genus of the tribe Sabethini up to the present known in 

 Africa, the midrib is well developed in the pupal paddles and there is a long terminal 

 seta, much longer than in the Culicini. Howard, Dyar and Knab believe that 

 " the greatest diversity among the pupae of mosquitoes will be found in the number 

 and arrangement of the setae on different parts of the body. These, we are sorry 

 to say, have not been adequately studied, but we are convinced that they will 

 furnish both generic and specific characters " ; and they point out that " there 

 is a well-marked difference in the two tribes above-mentioned. In the Sabethini 

 the seventh and eighth abdominal segments each bear a pair of ample fan-shaped 

 tufts at the apical angles ; these are absent in the Culicini." 



Bacot takes up the question of the " possibilities of the pupal paddles (anal 

 plates of Wesche) for purposes of classification and the separation of ill-defined 

 species " of mosquitoes in his " Report of the Entomological Investigation 

 undertaken for the Yellow Fever (West Africa) Commission " (pp. 140-146), stating 

 that " very marked differences may occur in the pupal paddles of closely related 

 species." Bacot qualifies this statement, however, by remarking that " there 

 seems ... no likelihood, so far as the scanty material examined goes, that these 

 characters could be made to afford the basis for an independent scheme of 

 classification." In the opinion of Bacot those appendages of the pupa which are 

 obviously likely to be adaptive rather than ancestral in character may form a 

 means of discrimination. 



